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Tropical Cyclone Iris weakened over the Coral Sea east of Queensland on Wednesday. At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone Iris was located at latitude 19.6°S and longitude 152.3°E which put it about 230 miles (370 km) east-northeast of Mackay, Australia. Iris was moving toward the east-southeast at 4 m.p.h. (6 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 990 mb.

An upper level ridge east of Australia was producing strong northwesterly winds which were blowing toward the top of Tropical Cyclone Iris. Those winds were causing strong vertical wind shear which weakened Iris on Wednesday. The stronger thunderstorms were occurring in bands southeast of the center of circulation. The bands in other parts of the circulation consisted primarily of showers and low clouds. The wind shear was not quite strong enough to blow the top off of the circulation, but the shear was preventing upper level divergence on the northern side of Tropical Cyclone Iris.

Tropical Cyclone Iris will move over water where the Sea Surface Temperature is near 28°C. So, there is enough energy in the upper ocean to support a tropical cyclone. However, the upper level ridge will continue to cause strong vertical wind shear and Tropical Cyclone Iris is likely to slowly weaken during the next several days.

Tropical Cyclone Iris is moving slowly toward the east-southeast. If the vertical wind shear blows the top half of the circulation away to the southeast, then Iris would be steered by the winds in the lower atmosphere. A high pressure system in the lower atmosphere over Australia would begin to steer Tropical Cyclone Iris back toward the northwest. On its anticipated track the center of Tropical Cyclone Iris is expected to remain east of Queensland. Rainbands on the western periphery have occasionally brought rain to the coast of Queensland, but most of the rain is falling over the ocean.

The proximity of Tropical Cyclone Iris prompted the Australian Bureau of Meteorology to issued Warnings and Watches for the east coast of Queensland on Monday. A Warning was issued for the portion of the coast from Ayr to Sarina including Mackay and the Whitsunday Islands. A Watch was issued for the portion of the coast from Sarina to St. Lawrence. At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Iris was located at latitude 17.1°S and longitude 149.0°E which put it about 210 miles (335 km) northeast of Townsville, Australia. Iris was moving toward the southeast at 3 m.p.h. (4 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 994 mb.

The circulation of Tropical Cyclone Iris was asymmetrical. Most of the showers and thunderstorms were located south and east of the center of circulation. The bands north and west of the center consisted primarily of low clouds and showers. Tropical Cyclone Iris was near the western end of an upper level ridge. The ridge was producing northwesterly winds which were blowing toward the top of the circulation. Those winds were producing moderate vertical wind shear and they were probably responsible for the asymmetrical distribution of thunderstorms.

Tropical Cyclone Iris will be moving through an environment marginally favorable for intensification during the next 48 hours. Iris will move over water where the Sea Surface Temperature is near 29°C. However, the upper level ridge will continue to produce moderate vertical wind shear. The shear will be strong enough to inhibit intensification. If the strength of the upper level winds slows, then Tropical Cyclone Iris could strengthen, but if the upper level winds get faster, then Iris will weaken. The forecast is for slow intensification, but there is high uncertainty about the intensity forecast.

The subtropical ridge east of Iris is steering Tropical Cyclone Iris slowly toward the southeast. A general motion toward the southeast is expected to continue for several more days. On its anticipated track the center of Tropical Cyclone Iris is expected to stay east of the coast of Queensland. However, Tropical Cyclone Iris could come close enough to the coast to bring gusty winds and locally heavy rain to locations under Warnings and Watches.

Tropical Cyclone Iris redeveloped east of Queensland on Sunday night. At 11:00 p.m. EDT on Sunday the center of Tropical Cyclone Iris was located at latitude 16.9°S and longitude 148.7°E which put it about 190 miles (310 km) east of Cairns, Australia. Iris was moving toward the southwest at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 995 mb.

Tropical Cyclone Iris formed over the Coral Sea last week but wind strong vertical shear quickly weakened Iris into an area of low pressure. The low pressure system meandered over the Coral Sea east of Australia during the past few days. More thunderstorms developed near the center of circulation on Sunday and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Iris again.

The circulation around Tropical Cyclone Iris was still reorganizing on Sunday night. A distinct low level center of circulation was evident on visible satellite images. More thunderstorms were developing near the center. A primary rainband wrapped around the northern, eastern and southern sides of the center of circulation. Bands northwest of the center consisted mainly of showers and low clouds. Storms near the core of the circulation generated upper level divergence which was pumping mass away to the east of the tropical cyclone.

Tropical Cyclone Iris will move through an environment somewhat favorable for intensification on Monday. Iris will move over water where the Sea Surface Temperature is 29°C. It is moving around the western end of an upper level ridge. The ridge is producing northwesterly winds which were blowing toward the top of the circulation. Those winds were causing moderate vertical wind shear and they may have been the reason for the lack of strong rainbands northwest of the center of circulation. The wind shear is likely to inhibit intensification, but it probably won’t prevent Tropical Cyclone Iris from intensifying on Monday.

Tropical Cyclone Iris was moving around the western end of a subtropical ridge which was steering Iris toward the southwest. Iris will likely move more toward the south and then southeast as it rounds the western end of the ridge. On its anticipated track Tropical Cyclone Iris is expected to remain east of Queensland.

Elsewhere over the South Pacific Ocean Tropical Cyclone Josie was swirling south of Fiji. At 11:00 p.m. EDT on Sunday the center of Tropical Storm Josie was located at latitude 21.1°S and longitude 178.1°E which put it about 185 miles (300 km) south of Suva, Fiji. Josie was moving toward the south-southeast at 14 m.p.h. (22 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 999 mb.

Tropical Cyclone Nora made landfall on the coast of Queensland near Pormpuraaw on Saturday. At 5:00 p.m. EDT on Saturday the center of Tropical Cyclone Nora was located at latitude 15.8°S and longitude 141.8°E which put it about 30 miles (50 km) south of Kowanyama, Australia. Nora was moving toward the south-southeast at 15 m.p.h. (24 km/h). The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h). The minimum surface pressure was 979 mb.

Tropical Cyclone Nora moved across the northern Gulf of Carpentaria and made landfall near Pormpuraaw earlier on Saturday. A weather station at Kowanyama, which is south of the original landfall recorded a sustained wind speed of 44 m.p.h. (70 km/h) and a wind gust of 62 m.p.h. (100 km/h). The station also recorded five inches (128 mm) of rain.

Tropical Cyclone Nora is forecast to move southward near the coast of the Gulf of Carpentaria for another 12 to 18 hours. Nora is then expected to move westward across the southern end of the Gulf of Carpentaria. The Australian Bureau of Meteorology was maintaining a warning for the portion of the coast from Pormpuraaw to Karumba. A Watch was in effect for the portion of the coast from Karumba to the border between Queensland and the Northern Territory. In addition to bringing gusty winds to the coast of Queensland, Tropical Cyclone Nora will drop locally heavy rain. The heavy rain could cause flash flooding in some places.

Tropical Cyclone Nora developed rapidly north of Australia over the Arafura Sea on Thursday. At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Nora was located at latitude 10.0°S and longitude 136.8°E which put it about 160 miles (260 km) north of Nhulunbuy, Australia. Nora was moving toward the east at 3 m.p.h. (5 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 986 mb.

A center of circulation organized quickly on Thursday in an area of thunderstorms over the Arafura Sea and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Nora. A primary rainband wrapped around the western and northern side of the center of circulation. An eye appeared to be forming at the center of Tropical Cyclone Nora. Bands of showers and thunderstorms were revolving around the core of the circulation. Storms around the core were generating well developed upper level divergence which was pumping mass away from the tropical cyclone. The removal of mass was allowing the surface pressure to decrease rapidly and the wind speeds were increasing in response.

The Australian Bureau of Meteorology issued Warnings for the portions of the coast from Elcho Island to Cape Shield including Cape Wessel and from Pormpuraaw to Thursday Island. A Watch was in effect for the portion of the coast from Pormpuraaw to the border between the Northern Territory and Queensland including Mornington Island.

Tropical Cyclone Nora will move through an environment very favorable for intensification during the next 48 hours. Nora will move over water where the Sea Surface Temperature is near 30°C. It will move through an area where the upper level winds are weak and there is little vertical wind shear. Nora is likely to intensify rapidly and it is likely to become the equivalent of a hurricane/typhoon within 24 hours. Tropical Cyclone Nora could become the equivalent of a major hurricane within 24 to 48 hours.

Tropical Cyclone Nora was moving through an area where steering winds are weak and it was moving slowly toward the east. A subtropical ridge east of Australia is expected to strengthen. The ridge is forecast to steer Nora more toward the south in 12 to 24 hours. On its anticipated track Tropical Cyclone Nora is expected to move over the Gulf of Carpentaria toward the coast of Queensland. Nora could strengthen into a dangerous tropical cyclone.

Elsewhere, Tropical Cyclone Marcus continued to churn west of Australia. At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Marcus was located at latitude 20.6°S and longitude 106.0°E which put it about 555 miles (895 km) west-northwest of Learmonth, Australia. Marcus was moving toward the south at 13 m.p.h. (21 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 951 mb.

Tropical Cyclone Marcus strengthened into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale as it churned northwest of Australia on Wednesday. At 5:00 p.m. EDT on Wednesday the center of Tropical Cyclone Marcus was located at latitude 15.8°S and longitude 108.0°E which put it about 600 miles (960 km) northwest of Learmonth, Australia. Marcus was moving toward the west-southwest at 14 m.p.h. (22 km/h). The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 195 m.p.h. (315 km/h). The minimum surface pressure was 918 mb.

After completing an eyewall replacement cyclone on Tuesday, Tropical Cyclone Marcus began to intensify quickly again on Wednesday. Marcus exhibited a circular, symmetrical circulation. There was a tiny circular eye at the center of circulation. The strongest winds were occurring in a ring of thunderstorms that surrounded the small inner eye. Recent satellite images suggested that another eyewall replacement cycle may be beginning. A larger, outer eyewall appeared to have encircled the small inner eye. Bands of showers and thunderstorms were revolving around the concentric eyewalls. Storms in the core of Marcus were generating very well developed upper level divergence which was pumping mass away in all directions from the tropical cyclone.

As frequently happens during eyewall replacement cycles, Tropical Cyclone Marcus increased in size after Tuesday’s eyewall replacement cycle was completed. Winds to hurricane/typhoon force extended out about 50 miles (85 km) from the center of circulation. Winds to tropical storm force extended out 180 miles (290 km) from the center. The Hurricane Intensity Index (HII) for Tropical Cyclone Marcus was 35.0. The Hurricane Size Index (HSI) was 18.7 and the Hurricane Wind Intensity Size Index (HWISI) was 53.7.

Tropical Cyclone Marcus is in an environment that is very favorable for strong tropical cyclones. Marcus is moving over water where the Sea Surface Temperature is near 30°C. It is moving through an area where the upper level winds are weak and there is little vertical wind shear. Although Tropical Cyclone Marcus is in a very favorable environment, another eyewall replacement cycle would cause it to weaken. The wind would begin to converge into the outer eyewall, which would cause the storms in the inner eyewall to weaken. The wind speeds would decrease as the inner eyewall weakens. Then the strongest winds would be found in the outer eyewall and the circulation would increase in size.

Tropical Cyclone Marcus is nearing the western end of a subtropical ridge over Australia. The ridge is steering Marcus toward the west-southwest, but the tropical cyclone will turn more toward the south when it reaches the end of the ridge. Tropical Cyclone Marcus will make a gradual turn toward the southeast during the next several days. On its anticipated track Tropical Cyclone Marcus will remain west of Western Australia during the next 36 to 48 hours.

Tropical Cyclone Marcus strengthened into the equivalent of a major hurricane on Monday. At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Marcus was located at latitude 15.0°S and longitude 117.7°E which put it about 340 miles (550 km) north of Port Hedland, Australia. Marcus was moving toward the west at 18 m.p.h. (29 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 955 mb.

The circulation of Tropical Cyclone Marcus was symmetrical and very well organized. A very small circular eye was at the center of circulation. A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of the circulation. Storms in the core were generating strong upper level divergence which was pumping mass away from the tropical cyclone. Winds to hurricane/typhoon force extended out about 60 miles (95 km) from the center of circulation. Winds to tropical storm force extended out about 190 miles (305 km) from the center.

Tropical Storm Marcus will continue to move through an environment very favorable for strong tropical cyclones during the next two days. Marcus will move over water where the Sea Surface Temperature is near 30°C. It is moving under an area where the upper level winds are weak and there is little vertical wind shear. Tropical Cyclone Marcus is likely to intensify and it could reach the equivalent of a Category 5 hurricane. If a rainband wraps around the core of the circulation, then a second eyewall could form. That would initiate an eyewall replacement cycle, which would cause Marcus to weaken at least temporarily.

Tropical Cyclone Marcus is moving around the western end of a subtropical ridge, which is steering Marcus toward the west. A general motion toward the west is expected to occur for anther 24 to 48 hours. Marcus will reach the western end of the ridge in about two days, and then the tropical cyclone will turn toward the south. On its anticipated track Tropical Cyclone Marcus will stay north of the coast of Western Australia for the next few days.

Tropical Cyclone Marcus moved back over the South Indian Ocean on Sunday and it strengthened rapidly north of Australia. At 11:00 p.m. EDT on Sunday the center of Tropical Cyclone Marcus was located at latitude 15.0°S and longitude 122.8°E which put it about 215 miles (345 km) north-northeast of Broome, Australia. Marcus was moving toward the west at 11 m.p.h. (17 km/h). The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h). The minimum surface pressure was 987 mb.

Tropical Cyclone Marcus weakened when it moved over the northernmost part of Western Australia, but it began to strengthen quickly after the core moved back over water. An eye rapidly reformed at the center of circulation. A ring of strong thunderstorms redeveloped around the eye and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of the circulation. Storms around the core were generating upper level divergence which was pumping mass away from the tropical cyclone. The circulation of Tropical Cyclone Marcus was relatively compact. Winds to tropical storm force extended out about 80 miles (130 km) from the center of circulation.

Tropical Cyclone Marcus will be moving through an environment very favorable for intensification during the next two days. Marcus will move over water where the Sea Surface Temperature is near 30°C. It will move through an area where the upper level winds are weak and there will be little vertical wind shear. Tropical Cyclone Marcus is likely to continue to intensify rapidly and it could become the equivalent of a major hurricane in 24 to 36 hours.

Tropical Cyclone Marcus is moving around the northern side of a subtropical ridge over Australia, which is steering Marcus toward the west. A general motion toward the west is forecast to continue for several more days. Tropical Cyclone Marcus will reach the western end of the ridge in two or three days. Marcus will turn toward the south at that time. On its anticipated track Tropical Cyclone Marcus will move farther away from the coast of Western Australia during the next two days.

Tropical Cyclone Marcus made landfall on the northern coast of Western Australia east of Kalumburu on Saturday night. At 11:00 p.m. EDT on Saturday the center of Tropical Cyclone Marcus was located at latitude 14.2°S and longitude 127.7°E which put it about 70 miles (115 km) east of Kalumburu, Australia. Marcus was moving toward the west-southwest at 10 m.p.h. (16 km/h). The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 85 m.p.h. (140 km/h). The minimum surface pressure was 984 mb. The Australian Bureau of Meteorology issued a Warning for the portion of the coast between Wyndham and Beagle Bay not including Wyndham or Derby.

Tropical Cyclone Marcus strengthened as it moved over the Timor Sea on Saturday. There was a small circular eye at the center of circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of the circulation. Storms in the core were generating upper level divergence which was pumping mass away from the tropical cyclone.

Tropical Cyclone Marcus will weaken on Sunday while the core of the circulation moves over the extreme northern part of Western Australia. Marcus is likely to strengthen when the center moves west of Kuri Bay and back out over water. The Sea Surface Temperature of the water west of Kuri Bay is around 30°C. The upper level winds will be weak and there will be little vertical wind shear. Marcus will likely intensify into the equivalent of a hurricane/typhoon after the center of circulation moves back over water.

Tropical Cyclone Marcus is moving north of a subtropical ridge over Australia. The ridge is steering Marcus to the west-southwest and that general motion is expected to continue for several more days. On its anticipated track Tropical Cyclone Marcus will move over the Mitchell Plateau toward Kuri Bay. Marcus will move away from the north coast of Western Australia when it moves west of Kuri Bay.

Tropical Cyclone Marcus brought wind and rain to Darwin, Australia on Friday night. A weather station at Darwin Harbor recorded a wind gust to 80 m.p.h. (130 km/h). At 11:00 p.m. EDT on Friday the center of Tropical Cyclone Marcus was located at latitude 12.7°S and longitude 130.7°E which put it about 20 miles (30 km) southwest of Darwin, Australia. Marcus was moving toward the southwest at 13 m.p.h. (21 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 80 m.p.h. (130 km/h). The minimum surface pressure was 982 mb. The Australian Bureau of Meteorology issued a Warning for the portion of the coast from Cape Hotham to Mitchell Plateau including Darwin and the Tiwi Islands. A Watch was issued for the portion of the coast from Cockatoo Island to Mitchell Plateau.

Tropical Cyclone Marcus intensified as it approached Darwin. An eye developed at the center of circulation and a ring of strong thunderstorms surrounded the eye. The strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of the circulation. Storms around the core were generating upper level divergence which was pumping away mass from the tropical cyclone.

Tropical Cyclone Marcus will move through an area favorable for intensification during the next 24 hours. Marcus will move over water where the Sea Surface Temperature is near 30°C. An upper level ridge over Australia is producing easterly winds which are blowing toward the top of the circulation. Those winds are creating some vertical wind shear, but the shear is not strong enough to prevent intensification. Tropical Cyclone Marcus could strengthen into the equivalent of a hurricane/typhoon when it moves over the Timor Sea on Saturday.

Tropical Cyclone Marcus was being steered toward the southwest by the ridge over Australia and the southwesterly motion is expected to continue. On its anticipated path the center of Tropical Cyclone Marcus will move across the Timor Sea on Saturday. Marcus could approach the north coast of Western Australia east of Kalumburu in about 24 hours.